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Topic: 17-40 Replacement (Read 5535 times)

When you do landscape shots, do you manually focus to infinity then stop down to f16? If you have never done it, try it. You will be surprised by how much the border and corner improves.

Reason? Canon's UWA zooms all suffer from severe field curvature. I have used all 4 of them: 17-40 f4, 17-35 f2.8, 16-35 f2.8 I and II, they all exhibit this. The field curves inward from center to corner, pretty heavily.

If you let the AF focus on center frame, the corner will be very out of focus. However if you manually focus to infinity, then corner focus plane will at least be pushed further and won't be so out of focus anymore.

I thought the 17-40 was a really good lens... Until I got the 24-70 mk2. I think of it as very capable now but it doesn't have the X factor of the 24-70 mk2- which I suspect is not dissimilar to the Zeiss 21...

The 17-40 can be good, but you have to stop down. Use it at 24-28mm and f/11 for good edge to edge sharpness. That's the case with other lenses as well (except Tilt- shift). Use it at f/11 - f/16 depending on the depth of field you need.

After f/11, all lenses are basically the same, because diffraction becomes the limiting factor, so don't expect a expensive lens to be noticeably better at f/16. Check the MTF charts at the test sites, the results start to equalize at f/8, by f/11 they are similar, and by f/16 they will be identical.

The beauty of a TS-E is that you can get a greater depth of field without stopping down so far, which means better results by using the optimum aperture. You can use that 17mm TS-e at f/8 or even a little wider aperture.

In any event, the point is that when you are doing landscape, you must stop down to get depth of field, and then spending $$$$ additional only gives a tiny bit of improvement, or virtually none at f/16.